1. Field of the Invention
The present invention relates to a slime-removing composition useful for paper manufacture. More particularly, the present invention relates to a slime-removing composition which has potent anti-bacterial and anti-fungal activity against a broad spectrum of microorganisms which causes the formation of slime on the process line of paper manufacture. Also, the present invention is concerned with a method for controlling the formation of slime during paper manufacture by use of the slime-removing composition.
2. Description of the Prior Art
In manufacturing paper, various raw materials and additives are used depending on the kinds of final products, and fundamentally, copious water is employed to mix the raw materials. This mixing process is conducted under a condition of 30xc2x0 C. and nearly neutral pH, which is suitable for microorganisms to grow. In addition, the materials used in paper manufacture are nutritious (in organic and inorganic aspects) enough for microorganisms to grow and proliferate, so that slime is formed periodically as a result of the inhabitation of microorganisms, disrupting the effective operation of paper manufacture. Particularly, microorganisms take advantage of various organic materials contained in white water for their proliferation, secreting polysaccharides. These polymeric materials secreted are combined with various organic and inorganic materials to form slime, a viscous mass. The slime is apt to form when the flow of fluid is weakened, especially on pipes or chests to which microorganisms readily adhere. The microorganisms causative of the slime formation are exemplified by bacteria, such as Pseudomonas spp. and Bacillus spp., which usually come from the air, clear water and recirculating white water, and by fungi, such as Aspergillus spp. and Candida spp., which usually come from additives used in paper manufacture, such as mineral slurries, paper coating agents, etc.
Recent changes in the conditions for paper manufacture have had a tendancy to aggravate the slime formation. For example, first, a high reuse rate of white water increases the quantity of the organic and inorganic materials dissolved therein and the temperature of the white water while decreasing dissolved oxygen, so that anaerobic microoganisms thrive to make the slime formation serious, giving offensive odor. Next, shortening or lengthening of the purging interval during the paper manufacture brings about an increase in the quantity of organic and/or inorganic materials accumulated, aggravating the slime formation. Finally, the recycling of waste paper makes the microbes flourish because the waste paper itself can be used as a nutrient of the microbes. Further, the remains of additives used in the recycling of waste paper lead slime-controlling agents to inactivation, resulting in the aggravation of the slime formation.
Accumulation of slime on paper-manufacturing process lines causes fouling, plugging, deposition and odors so as to lower the productivity and workability of paper manufacture, discolor the final products, and make them more impure and offensively odorous. Above all, most problematic are the deterioration of pulp and the occurrence of paper cutting which causes the interruption of operation, giving rise to a waste of time and a reduction in equipment efficiency. In result, the accumulation of slime incurs a significant economical loss directly and indirectly.
As mentioned above, examples of the microorganisms which can form slime on paper manufacturing lines are various, including bacteria, such as Pseudomonas spp. and Bacillus spp., and fungi, such as Aspergillus spp. and Penicillium spp. In order to control such slime-causing microorganisms, isothiazoline-based or brome-based compounds have been conventionally used as slime-removing agents. These slime-removing agents based on single compounds, however, are not superior in rapid antibacterial and antifungal activity nor potent in sterilizing activity against a broad spectrum of a bacteria and fungi. For example, as for 2,2-dibromo-3-nitrilepropionamide (DBNPA), which is a brome compound, an amount of 5 ppm is necessary for showing the sufficient sterilizing activity after 24 hours, but elicitation of early sterilization (after 3 hours) requires an amount of 50 ppm (Society for Antibacterial and Antifungal Agents, Japan, Antibacterial and Antifungal Agent Dictionary p142, 1986). Isothiazoline compounds, when being used alone for a long period of time, have a side effect of mutating the slime-causing microorganisms, especially such as Pseudomonas spp., into resistant ones to increase the slime formation. To solve this problem, various slime-removing agents are in turn used or gradually higher concentrations thereof are added with more frequent addition rounds. However, the employment of various slime-removing agents is somewhat cumbersome and the workers come to be exposed to more dangerous conditions when higher concentrations are added. During the operation of paper manufacture processes, moreover, the slime-controlling agents added become poor in rapid action and persistency due to the continuous stream characteristic of paper manufacture. This problem can be avoided by feeding slime-controlling agents into two or more sites of the process line or at higher concentrations. However, this physical management is accompanied by the lowering of productivity and workability and the incurrence of an economical loss.
Polyhexamethyleneguanidine phosphate is an antimicrobial agent which is of excellent rapid action and low toxicity without giving odor, but is found to be relatively poor in the persistency of antimicrobial activity.
Leading to the present invention, the intensive and thorough research on the removal of slime formed on paper manufacture process lines, repeated by the present inventors aiming to kill slime-causing microorganisms with economical effectiveness, resulted in the finding that a combination of polyhexamethyleneguanidine phosphate and 2-bromo-2-nitro-1,3-propanediol shows effective antimicrobial activity against a broad spectrum of microbes, including bacteria and fungi, with excellency in both rapid antimicrobial activity and persistency.
Therefore, it is an object of the present invention to provide a slime-removing composition useful for paper manufacture, which is of low toxicity with high sterilizing activity against a broad spectrum of microorganisms, including bacteria and fungi.
It is another object of the present invention to provide a method for controlling slime by means of such a composition.
In accordance with an embodiment of the present invention, there is provided a slime-removing composition useful for paper manufacture, comprising a mixture of polyhexamethyleneguanidine phosphate and a 2-bromo-2-nitro-1, 3-propanediol, represented by the following formulas I and II, respectively, at a weight ratio of 1:1 to 1:16 polyhexamethyleneguanidine phosphate:2-bromo-2-nitro-1, 3-propanediol. 
wherein m is an integer of 4 to 7 and n is an integer of 1 to 14.
In accordance with another embodiment of the present invention, there is provided a method for controlling the formation of slime in paper-manufacturing processes, in which the slime-removing composition is fed an amount of 20 to 1,000 ppm with intervals of 8 to 24 hours to the pipes and chests of the paper-manufacturing processes.
In the present invention, a slime-removing composition is prepared by mixing a polyhexamethyleneguanidine phosphate of Formula I with 2-bromo-2-nitro-1,3-propanediol of Formula II at a weight ratio of 1:1 to 1:16. When the weight ratio of 2-bromo-2-nitro-1,3-propanediol to polyhexamethyleneguanidine phosphate is below 1 or over 16, the resulting slime-removing compositions are poor in sterilizing activity against microorganisms causative of slime. The slime-removing composition of the present invention may exist in a powder phase or a liquid phase. A powder phase of the slime-removing composition can be obtained by mixing polyhexamethyleneguanidine phosphate powder and 2-bromo-2-nitro-1,3-propanediol powder at a weight ratio of 1:1 to 1:16. As for the liquid phase, an aqueous solution comprising 25 wt % of polyhexamethylene phosphate may be combined with an aqueous solution comprising 25 wt % of 2-bromo-2-nitro-1,3-propanediol at a weight ratio of 1:1 to 1:16 polyhexamethyleneguanidine phosphate:2-bromo-2-nitro-1,3-propanediol.
To obtain maximal sterilizing effects, the slime-removing composition of the present invention is fed where slime is formed frequently, with unaided hands or with the aid of an automatic scale feeder. The slime-removing composition is preferably fed at an amount of 20 to 1,000 ppm. For example, when the amount of the slime-removing composition is below 20 ppm, the sterilizing effect on the slime-causing microorganisms is not large enough to kill the microorganisms. On the other hand, larger than 1,000 ppm of the slime-removing composition has a negative influence on the safety and workability of workers. Preferable amounts of a powder of the slime-removing composition fall within the range of 20 to 200 ppm and when existing as a liquid phase, the composition is preferably added at an amount of 50 to 1,000 ppm.
It is recommended that the slime-removing composition of the present invention be used at intervals of 8 to 24 hours lest resistant strains should be effectively prevented from occurring upon long-term use.
The slime-removing composition of the present invention finds the application of regulating microorganisms in the various industries including cooling water and sterilizer industries in addition to paper and pulp making industries. Particularly, the slime-removing composition of the present invention is useful for paper manufacture and may be used as an antiseptic or preservative for additives useful in paper manufacture.